The tendency of fire and wind is to ascend upwards from the depths of the earth toward the sky. The tendency of water and earth is to descend from the sky to the midpoint of the sky, [i.e., the center of the Earth,] for the midpoint of the sky is the lowest point, below which nothing is lower. These tendencies are not a conscious matter, nor are they willful. Rather, it is a pattern affixed within them and a nature they were given.
The natural characteristics of fire are that it is warm and dry. It is the lightest of all [these fundamental elements]. Wind is warm and moist. Water is cold and moist, and earth is dry and cold. It is the heaviest of all [these fundamental elements].
Water is lighter than earth. Therefore, it is found above it. Wind is lighter than water. Therefore, it hovers above it. Fire is even lighter than wind.
Since these are the fundamental [elements] for all the bodies below the sky, the matter of every single body - man, animal, beast, fowl, fish, plant, metal, and stone - is a combination of fire, wind, water, and earth. [In the process of] the combination of these four, each one of them changes while they are being combined. Thus, the combination of the four [fundamental elements] does not resemble any one of the [elements] as it exists alone. [Similarly,] in any combination of them, there cannot be found even one portion of fire as it exists alone, wind as it exists alone, water as it exists alone, nor earth as it exists alone. Rather, they have all changed and become a single body.
Each and every body which is a combination of these four [fundamental elements] will have a combination of cold and warmth, moistness and dryness. There are some bodies which have a more powerful [concentration] of the fundamental [element] of fire - for example, creatures with living souls. Accordingly, they have a higher temperature. [Conversely,] there are some bodies with a more powerful concentration of the element of earth - for example, the stones. Accordingly, they are very dry. Similarly, some of them have bodies with a greater concentration of the element of water. Accordingly, they are moist.
In this manner, one may find one body which is warmer than another body, which is itself warm, and one body drier than another body, which is itself dry. Similarly, there are bodies in which cold alone is noticeable, and other bodies in which moistness alone is noticeable. In some bodies, cold and dryness are equally noticeable; in others, warmth and dryness are equally noticeable; in others, warmth and moistness are equally noticeable; and in others, warmth and moistness are equally noticeable. According to the predominance of the element that is found in the essential combination, the inclination and nature of that element will be expressed in the body [resulting from] a mixture [of all the elements].